Firing with powdered fuel



April 8 1924.

W. R. WOOD FIRING WITH POWDERED` FUEL Filed May l1. 1925,m//////////W///// I Patented Apr. td, lge.

WEIRD) RUTHERY "WD, F LN'DQN, ENGLAND.

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Application led May .l, i923. Serial No. 638,357.

ments Relating to Firing with Powdered Fuel, of which the :following isa specification.

burning powdered fuel in a heating furnace such as a boiler furnace andhas for its ob- .ject to dry the fuel on its way to the pul-v verizerbymeans of thewaste gases or the furnace.

ln order that the temperature of the furnace gases may be sufficientlyunder control provision is made for mining air with the turnace gasesbefore they are passed over the fuel. F or it will be obvious that i 2oif the temperature of the coal were raised to that at which incipientcarbionizatiou occurs, combustible matter would be lost unless thefurnace gases were returned through the :furnace after they hadtraversed the coal, which would defeat one ot the objects' of 'theinvention, namely keepin cutoff' the furnace the water in the fuel.nother object of mixing airl with the 'furnace gases is.

to dilute them in respect of their content oi water vapour, or, in moreexact language, to diminish the partial pressure of the water vapourwhich 'they carry as a productor combustion of the fuel. The lower suchpartial pressure, the greater the drying capacity of the gases.

Another object of the invention is to avoid the nuisance created bydelivering dust laden gases into the atmosphere at 'alow level. :lnpassing through the coal to be dried the gases take up 'from the coal a`portion et dust which, although quite small when considered as lostfuel is sutilciently important when considered as dust in dischargedgases. rlhe invention avoids this objection by returning the gases whichhave passed through the fuel, to the flue of the furnace. By thisexpedient the dust is in part deposited after the manner of Hue dustgenerally and in part dissipated atehigh level with the main volume offlue gases.

'lfo ensure satisfactory working it is generali best to withdraw the hotgases trom the `ue by means of a fan or the like.

ln the accompanying drawings Fig. l is a diagram representing a boilerfurnace inlil This invention relates to improvements in' chamber a andback through the slotted lowstallation to which the invention isapplied, and Fig. 2 illustrates a modification.

Referring to F ig. l of the drawings, a indicates a vertically disposeddrying chamber, provided with aV centrally disposed -Tf chute .Zextending longitudinally thereof, through which chute the fuel is led tothe hopper la of a pulverizer Z. The portion ol the chute Z; within thechamber a is provided with multiple openings,` preferably dened by aseries of slats or bars in louver "termation, to admit Afree circulationoivgaseous drying media to and through the chute.

Leading into the upper part of the chamber a is a` pipe e which isconnected to the chimney or ilue d ot the furnace or other heating unitin which the fuel is to be burned and near the bottom 'oit the chambero, there is connecting a pipe e which leads baclr into the chimney ordue d, the latter pipe beingprovided with a suction tan g and eregulating damper it., The pipe e is provided with a gate or damper fcooperating with an ,air inlet in the wall ol the ipe, by means of`which an accurately regu ated supplyot air may be admitted to the ipeand admired with the tlue gases or pro ucts of combustion before lthelatter enter the drying chamber. ln order to cause" the mirture of luegases and tempering air to pass at leastA twice through the body' offuel being fed through the chute h, a balde c is disposed between thechute and wall et the chamber av and between the discharge end of pipe eand the intake end et' pipe e', so that the gases will pass transverselythrough the slotted openings in the upper part of the chute and in areverse direction in the lower part of the chute, as indicated by thearrows. p

The operation of the apparatus is as follows: rThe coal is fed into thetop of the drying chamber through the chute 'o and the products ofcombustion or Jfurnace gases are taken from vthe flue or chimney dthrough fl the pipe c, delivered into the upper part ol the chamber a,and passed transversely through the openings in the chute d and the fuelin the latter, thence downward in the er end of the chute and the fueltherein to the exhaust pipe e' back to the chimney. The furnace gaseswould, under ordinary conditions, be ot too high a temperature to ladmit to the drying chamber, and would @llt be liable to cause incipientcombustion of the fuel and would poibly produce an explosion if anymaterial amount of the fuel were in a highly pulverized or comminutedcondition, and in order to prevent these contingencies the temperatureof the i furnace gases and any ine'particles of fuel which may be takenup t ereby into the chimney or stack d. .The particular advantages ofthis coordination of a paratus, are that the fuel will be effective ydried before reaching the pulverizer and the moisture and the dryingmedium separated, from the fuel and diverted into the chimney or stack,so that neither the moisture content of the fuel nor the furnace gasesare delivered, in any appreciable quantities to the furnace, but, on thecontrary, the completely dried and pulverized fuel is delivered to thefurnace in the best possible condition to effect complete combustion. Itwill be understood that any appropriate means for feeding the comminutedfuel from the pulverizer to the furnace may be employed and thatillustrated in Fig. 1 is merely exemplary, the same comprising a screwconveyer 'm for delivering the pulverized fuel from the pulverizer l toa feed chute n, which latter' is provided with a brushA or similarpropellin device p near its lower end which isr e ective in pro'ectingthe wdered fuel through the fue opening 0 1n the furnace wall.

Theconstruction shown in Fig. 2 is similarl in -all respects to thatillustrated in Fig. 1, except that the suction fan g and the damper hfare located in the pipe e supplying the furnace gases to the dryingchamber, thls arrangement being preferred where it is found desirable tocontrol the gases entering the drying chamber. In each case, however,the dampery or valve f is adjusted to admit the desired proportion ofair to the furnace gases, as hereinbeforel explained, and the damper hor la. is operated to control the total volume of gases passing'throughthe drier. These vadjustments necessarily are made with reference to theproportion.

of moisture in the fuel and also the nature of the latter in respect tothe temperature at which it loses Iits hydro-carbon vapors, as will beunderstood.

What I claim is: 4

The method of Ipreparing and burning fuel, which comprises feeding thefuel to a. drier, passing the products of combustion from the furnace inwhich burning is effected through said drier, admixing air with theproducts of combustion in quantities suflcient to reduce the temperatureof the llatter below the combustion point of the fuel plrior to theadmlssion of said products to t e drier, separating the dryin mediumfrom the fuel, pulverizlng the fue and feeding the dried and pulverizedfuel tothe furnace.

In testimony whereof, I name to this specification.

WILFRED RoTHERY Woon.

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